Binder systems derived from amorphous silica and bases

ABSTRACT

The present invention relates to compositions comprising the reaction product of amorphous silica or ultra-fine silica and one or more bases. The present invention also relates to materials and method involving the use of such products. In particular, the present invention i.a. relates to new mineral wool products, e.g. products comprising man-made vitreous fibres (such as glass fibres, slag fibres, stone fibres and rock fibres) or perlite, having included therein a binder component which comprises amorphous silica and alkali metal organosiliconates, e.g. potassium methyl siliconate. An important feature of such products is the preparation of the binder systems under vigorous mixing. Such products provide good fire, heat and sound insulating properties. The present invention also provides to a method for removing odorous substances from a gas where materials prepared from ultra-fine silica, water, and one or more components enabling porosity-conferring binding of the material, e.g. a base or bases. Furthermore, the invention provides methods for thixotroping bitumen.

This application is a Continuation of co-pending application Ser. No.09/830,701 filed on Apr. 30, 2001 and for which priority is claimedunder 35 U.S.C. § 120. Application Ser. No. 09/830,701 is the nationalphase of PCT International Application No. PCT/DK99/00588 filed on Oct.29, 1999 under 35 U.S.C. § 371. The entire contents of each of theabove-identified applications are hereby incorporated by reference. Thisapplication also claims priority of Application No. PA 1998 01400 filedin Denmark on Oct. 30, 1998 under 35 U.S.C. § 119.

FIELD OF THE INVENTION

The present invention relates to compositions comprising the reactionproduct of amorphous silica or ultra-fine silica and one or more bases.The present invention also relates to materials and method involving theuse of such products.

In particular, the present invention i.a. relates to new mineral woolproducts, e.g. products comprising man-made vitreous fibres (such asglass, slag, stone and rock fibres), having included therein a bindercomponent which comprises amorphous silica and alkali metalorganosiliconates. The present invention also relates to the bindersystems as such.

Furthermore, the present invention relates to a method for removingodorous substances from a gas where materials prepared from ultra-finesilica, water, and one or more components enabling porosity-conferringbinding of the material, e.g. a base or bases.

BACKGROUND OF THE INVENTION

In the field of mineral wool product there has been an increasinginterest in replacing organic binders such as phenol formaldehydebinders. Organic binders may however be inflammable. Thus, there is adesire for new essentially fire-proof binder systems for mineral fibreproducts.

JP 51 075 732 (WPI Derwent Abstract No. 76-62407x) relates to acorrosion protecting agent. Powdered zinc is mixed with a binderconsisting of silica colloid and a water-soluble metal organosiliconate,e.g. sodium methyl siliconate, sodium ethyl siliconate or sodium phenylsiliconate, etc.

RU 2 057 098 (WPI Derwent Abstract No. 96-517000) relates to a mixturefor surface coating of concrete, which comprises cement, a mineralfiller, micro-silica, a superplasticiser, a moisture repelling organicsilicon fluid based on sodium siliconates and poly-hydrosiloxanes, andwater.

RU 2 014 306 (WPI Derwent Abstract No. 95-036343) relates to acomposition comprising a gypsum-cement-pozzuolana binder, perlitehydrophobised with sodium methyl siliconate, glass fibres, and water foruse as heat- and sound-insulating articles. The composition comprise asmall amount of milled glass fibres.

DESCRIPTION OF THE INVENTION

Binder Systems Comprising Amorphous Silica and One or More Bases,Preferably Alkali Metal Organosiliconate

The present invention i.a. provides new and advantageous mineralfibre/particles products based on an interesting binder system includinga large amount of an amorphous silica.

All percentages are in percent by weight, unless otherwise stated.

Thus, the present invention provides an water-based binder system beingderived from amorphous silica, one or more bases, and optionallyadditives. Preferably, the binder system is derived from amorphoussilica, at least one of (a) an alkali metal organo-siliconate and (b) abase, and optionally additives.

In the presently most interesting variant, the binder system comprisesan alkali metal organosiliconate as a mandatory constituent.Alternatively, the binder system comprises a base as a mandatoryconstituent. A number of relevant and interesting embodiments of thebinder system of the present invention comprises an alkali metalorganosiliconate as well as a base.

Where the binder system comprises an alkali metal organosiliconate as amandatory constituent, the weight ratio between the amorphous silica andthe organosiliconate(s) in the binder system is preferably in the rangeof 99:1 to 75:25.

A number of different well-known materials can constitute the amorphoussilica part of the binder system. Industrially produced amorphoussilicas can be divided into at least four groups: silica gel, colloidalsilica, precipitated silica and pyrogenic silica. Examples of suchsilicas are Aerosil®, Ketjensil®, Carbosil®, Cabosil®, ElkemMicrosilica®, etc. Furthermore, other relevant amorphous silicas are ofnatural origin among which puzzolanes, Fuller's Earth, bentonite,fly-ash, tuff, pimpstone, etc.

Typically, relevant amorphous silica materials are materials notexclusively being constituted by SiO₂. Thus, it is generally believedthat a certain amount of other inorganic impurities may be acceptablefor the purposes described herein. However, the amorphous silica shouldcomprise at least 60%, such as at least 70%, preferably at least 80%, inparticular 90%, by weight of SiO₂.

The amount of silica (solids) in the binder system is preferably atleast 50%, such as 60-99%, e.g. 65-95%, in particular 70-95%, by weightof the non-aqueous constituents.

It is presently believed that one of the important properties of thesilica to be used within the present invention is the particle sizewhich preferably should be in the range of 0.001-20 μm, such as 0.01-0.5μm, in particular 0.05-0.1 μm. It is also presently believed that thespecific surface area of the silica should be in the range of 1-1500m²/g, such as 10-1000 m²/g, typically 10-500 m²/g, presently preferred10-100 m²/g.

It is presently contemplated that ground (non-amorphous) silicamaterials, e.g. ground sand, may be used as long analogous withamorphous silica as long as the specific surface of such materials isabove 10 m²/g.

The amorphous silica is preferably provided in the form of a slurry, inparticular with due regard to the below-mentioned process for preparingthe binder system. Slurries of silica to be used within the presentinvention should preferably comprise 20-80% by weight of silica.

The alkali metal organosiliconate is preferably selected from sodium andpotassium salts of an organosiliconate selected from methyl siliconate,ethyl siliconate, propyl siliconate, butyl siliconate and phenylsiliconate, preferable potassium methyl siliconate.

When present, the amount of alkali metal organosiliconate (solids) istypically 1-25%, such as 2-20%, in particular 2-15%, by weight of thenon-aqueous constituents.

The alkali metal organosiliconate is also often provided as an aqueoussolution. The alkali metal organosiliconate content of such solutions istypically 1-80% such as 10-50%, preferably 20-45%, by weight. Examplesof commercially available organosiliconates are Wacker BS-15 (42%aqueous solution of potassium methyl siliconate) and Wacker BS-20.

It should be understood that even though reference is made to “a” silicaand “an” alkali metal organosiliconate, each of those components as wellas the base (see below) may actually be constituted by two or moredifferent products or starting material so as to form a mixture of theconstituent in question which fulfils the requirements (amount,qualities, etc.) defined herein. Thus, the silica constituent may beformed by two different silica qualities having different particle sizedistributions and/or the base constituent may be formed by, e.g. aliquid and a solid base component (e.g. hydroxides and cements).

In the events where a base (other than the alkali metalorganosiliconate) is included either as a mandatory or as an optionalconstituent, such a base is preferably selected from alkali or alkalineearth metal hydroxides, such as sodium hydroxide, potassium hydroxide,magnesium hydroxide, and calcium hydroxide, alkali or alkaline earthmetal silicates, aluminium silicates, iron(I) and iron(III) silicatesand mixtures thereof, alkali or alkaline earth metal pyrosilicates,aluminium pyrosilicates, iron(II) and iron(III) pyrosilicates andmixtures thereof, alkali or alkaline earth metal carbonates, alkali oralkaline earth metal bicarbonates, alkali or alkaline earth metalphosphates, alkali or alkaline earth metal pyrophosphates, ammonia, andorganic amines, such as primary, secondary, and tertiary amines, e.g.,methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine,triethylamine, and anilines, such as aniline, methylaniline anddimethylaniline, and cements (alkaline cements), such as basic Portlandcement, rapid Portland cement, high early strength Portland cement,sulphate resistant cement, low-alkali cement, low heat cement, whitePortland cement, Portland blast furnace cement, Portland pozzolanacement, Hasle cement, ultra Cement and aluminate cement (high aluminacement) and combinations thereof. In particular, the base or basesis/are selected from alkali metal hydroxides, alkaline earth metalhydroxides and cements, preferably selected from sodium hydroxide,potassium hydroxide and calcium hydroxide. As can be seen from theexamples, a combination of two or more bases can also be used, even withcertain advantages.

When present, the amount of base is typically up to 39%, such as 1-33%,in particular 2-28%, by weight of the non-aqueous constituents.

When the base is cement, interesting foamy materials can be formedsimply by mixing amorphous silica and cement slurries under vigorousmixing. The weight ratio between amorphous silica and cement istypically in the range of 80:20-50:50. Such products and their uses asinsulating materials represent a further aspect of the presentinvention.

It is generally believed that the highest degree of hydrophobicity ofthe products of the present invention (see below) can be accomplished byusing a larger amount of the alkali metal organosiliconate than thebase, in particular when alkali metal organosiliconate is used alone. Inthe embodiments where a siliconate as well as a base is present, theweight ratio between alkali metal organosiliconate and base ispreferably 10:1-1:10 such as 5:1-1:5.

The total amount of alkali metal organosiliconate and base willdetermine the degree of reaction of the amorphous silica. It is believedthat advantageous properties—in particular with respect to the silica“egg” theory, vide infra—are obtained when the total amount of alkalimetal organosiliconate and base it below the stoichiometric amountneeded to react with all amorphous silica. It is believed that thestoichiometric ratio between amorphous silica and the total amount ofalkali metal organosiliconate and base should be less than 1:1, such asin the range of 1:0.95-1:0.4, in particular 1:0.9-1:0.5.

It is presently believed that excess of the siliconate and the base(after reaction with the silica) should be avoided in order to avoidhygroscopic carbonates.

Furthermore, the mixture from which the binder system is derived mayfurther comprise one or more additives (additional non-aqueousconstituents). Such additives may be any other components used to modifythe properties of the resulting binder system or of any products havingthe binder system included. Examples of additives are surfactants, smallamounts of organic solvents (even though generally undesirable forhealth and safety reasons), accelerators and retarders (accelerators andretarders: only when the base is a cement), etc. Examples of surfactantsare non-ionic, anionic, and cationic surfactants. Examples of suitablesurfactants are e.g. anionic surfactants such as derivatives of fattyacids wherein the negative charge is provided by a free carboxyl group,a sulphonate group, or a phosphate group, and such anionic surfactantscommonly used in rinse aids; non-ionic surfactants such as esters orpartial esters of fatty acids with an aliphatic polyhydric alcohol suchas e.g. ethylene glycol, glycerol, sorbitol, etc., and thepolyoxyethylene and polyoxypropylene derivatives of these esters, andsuch non-ionic surfactants commonly used in rinse aids; cationicsurfactants such as derivatives of fatty acids, wherein the positivecharge is provided by one or more quaternary ammonium groups, and suchcationic surfactants commonly used in detergents. Fatty acids typicallycontain from 6 to 22 carbon atoms; examples are caproic, octanoic,lauric, palmitic, stearic, linoleic, linolenic, olesteric, and oleicacid, etc. Examples of applicable accelerators are e.g. calcium formate,calcium chloride, alkali metal nitrates, and ammonium nitrates. Examplesof suitable retarders are polyhydroxycabocide, and alkali or alkalineearth metal phosphates. Small amounts of solid constituents (preferablyless than 5%) may also be used as additives; examples of such solid“additives” are ultra-fine fibres, flakes, mica, etc.

The total amount of additives is typically 0-10%, such as 0-5%,preferably 0-3%, by weight of the non-aqueous constituents. Whenpresent, the amount is typically at least 0.01% by weight of thenon-aqueous constituents.

Such additives may be vigorously mixed together with the alkali metalorganosiliconate and base or may be added after the vigorous mixing as afinal conditioning of the binder system. It is presently preferred thatany additives are added together with the siliconate and base beforemixing of those.

In one particularly interesting embodiment, the mixture from which thebinder is derived is an water-based mixture of amorphous silica, analkali metal organosiliconate, optionally a base, and optionallyadditives, where the amorphous silica constitutes 60-99%, preferably65-95%, in particular 70-95%, the organosiliconate constitutes 1-25%,preferably 2-20%, in particular 2-15%, the base constitutes 0-39%,preferably 1-33%, in particular 2-28%, and any additives constitutes atotal of 0-10%, preferably 0-5%, in particular 0-3%, by weight of thenon-aqueous constituents.

The present invention also provides a method for preparing a bindersystem as above, preferably a binder system derived from a mixturecomprising amorphous silica, at least one of (a) an alkali metalorganosiliconate and (b) a base, and optionally additives, the methodcomprising vigorously mixing an aqueous slurry of the amorphous silicawith the at least one of (a) an alkali metal organosiliconate and (b) abase, and the optional additives, said mixture having an initial pH inthe range of 11.5-14 and a final pH in the range of 7.5-11.0.

It is preferred that the vigorous mixing of silica, the at least one of(a) an alkali metal organosiliconate and (b) a base and the optionaladditives is performed using a high-speed mixer so as to obtain asubstantially uniform mixture of reacted silica particles, said silicaparticles being at least partially, but not fully, reacted with the atleast one of (a) an alkali metal organosiliconate and (b) a base.

By vigorous mixing is meant that the mixing is mechanical mixing with anapplied energy of at least 0.001 kWh/kg binder system (including water),such as at least 0.005 kWh/kg binder system, e.g. in the range of 0.01-1kWh/kg binder system. Preferably, mixing is completed within one hour,in particular within 15 min.

In the events where the binder system comprises an alkali metalorganosiliconate as well as a base, it is possible to first mix thesilica and the base under vigorous stirring and then afterwards add thesiliconate. Alternatively, a part of the silica may be mixed with thebase and another part of the silica may be mixed with the siliconate,both under vigorous stirring. It is contemplated that thesemodifications may provide various advantageous properties depending onthe purpose of the binder system. In one variant, the silica is mixedwith the base and is stored for 1-36 hours before addition of the amountof siliconate constituent. This allows for the preparation of aexcellent binder system.

As should be understood that the remainder of the binder system iswater. The above-mentioned amounts of non-aqueous constituents may beobtained directly by using the indicated amounts before mixing.Alternatively, the binder system may be diluted by addition of furtherwater. Also, excess water may be removed after preparation, but beforeuse of the binder system. It is preferred that the amount of non-aqueousconstituents is in the range of 5-40% by weight, such as 7-30% byweight, of the water-based binder system.

Furthermore, it is also preferred that the viscosity of the resultingbinder system—before application onto any mineral fibre and/or mineralparticle material—is in the range of 1-500,000 cp, in particular in therange of 1-30,000, especially in the range of 10-30,000 so as tofacilitate application of the binder, e.g. by spraying (typicallyrequires a viscosity in the range of 1-10,000), brushing or dipping. Asuitable viscosity may be obtained by addition of additional waterbefore application, vide supra.

Also preferred are binder systems where the pH is in the range of7.5-11.0. The pH value may be adjusted by dilution with water.

Without being bound to any specific theory, it is believed that thepresent invention is particularly interesting and relevant where thepreparation of the binder system is conducted in such as way that theamorphous silica is only partially reacted and dissolved, i.e. so thatthe at least a part of the fine particles is unreacted after treatmentwith the alkali metal organosiliconate and/or base, although some of thesmallest particles may be fully reacted. When view in another way, it isbelieved that the silica particles are partially reacted with thesiliconate and/or base so as to have a sticky surface just as frog eggs.When applied to a batch of mineral fibres and/or mineral particles, itis believed that the silica “eggs” after curing will provide furtherstability to the fibre web or bundle, which will result in improvedform-stability. The preliminary theory is supported by the fact that theresults obtained when using a binder system prepared from silica andpotassium hydroxide (stoichiometric ratio 1:<1) provides better resultsthan a comparative binder system constituted by potassium water glass.This being said, a variant where the silica is fully dissolved is alsocontemplated within the present invention.

This suggested structure of the binder—which is normally applied to amineral material in the form of a “solution” or probably rather as a“slurry”—has resulted in the remarkable advantages of the present bindersystem over previous binder systems used in connection with mineralfibres and mineral particles.

What appears to be a remarkable feature of the present invention is thefact that two non-film forming components (i.e. the siliconate and thesilica slurry) are mixed to give a film-forming product (the binder).

According to the object of the present invention, the binder system isused in combination with mineral fibres and/or mineral particles.Mineral materials in the form of fibres or particles should be inorganicmaterials such as mineral fibres such as volcanic rock fibres,wollastonite fibres, montmorillonite fibres, tobermorite fibres, biotitefibres, atapulgite fibres, calcined bauxite fibres, etc., mineral wool,whiskers, sand, expanded clay, wollastonite, perlite, ceramic fibres,Leca®, any man-made vitreous fibre, glass fibres including micro glassfibres, Rockwool® fibres, processed mineral fibres from mineral wool,and also inorganic fillers such as crushed minerals or otherfine-grained minerals.

Thus, the present invention also provides a mineral fibre/particleproduct comprising mineral fibres and/or particles and a binder system,said binder system being derived one or more bases, preferably from amixture comprising amorphous silica and at least one of (a) an alkalimetal organosiliconate and (b) a base, and optionally one or moreadditives. The binder system is essentially as described above.

It should be understood that the product may comprise mineral fibres,mineral particles as well as combinations of mineral fibres and mineralparticles, thus the nomenclature fibre/particles. Preferably, theproduct is a mineral fibre product, in particular product comprisingman-made vitreous fibres. A mineral fibre product may comprise a smallproportion of particles, e.g. up to 15%, such as up to 10%, preferablyup to 5%, by weight of particles, and vice versa for mineral particleproducts.

Consequently, the present invention also provides a method for preparinga mineral fibre/particle product, preferably a mineral wool product,comprising mineral fibres and/or mineral particles and a binder system,said binder system being derived from one or more bases, preferably froman aqueous mixture of amorphous silica, at least one of (a) an alkalimetal organosiliconate and (b) a base, and optionally additives, themethod comprising the step of:

-   preparing a binder system by mixing an aqueous slurry of the    amorphous silica, with the one or more bases, preferably the at    least one of (a) an alkali metal organosiliconate and (b) a base,    and the optional additives,-   applying the binder system to the mineral fibres and/or mineral    particles, and drying and curing the binder so as to obtain the    mineral fibre/particle product.

Although mineral fibre products presently are the most interesting,mineral particle products based on perlite constitute a similarlyinteresting embodiment due to the excellent insulating properties, i.e.heat, sound, and fire insulating properties observed so far (see theexamples). It is believed that compositions where the weight ratiobetween the binder system (solids) and perlite is in the range of4:1-1:4 such as 4:1-1:3 are particularly interesting. The binder systemis as defined and specified above.

The preparation of the binder system is accomplished as described above.The application of the binder system to the mineral fibres and/orparticles can be accomplished by application means known to the personskilled in the art, e.g. by dipping, spraying, by means of a brush or aroller or a blade, etc.

The drying and curing step should always (as will be apparent to theperson skilled in the art) be conducted with due regard to the nature ofthe constituents of the binder system and the mineral fibres/particle,however in the following will be given general guidelines for the dryingand curing step. It should be noted that drying and curing is generallyconsidered as one step as the drying (removal of water) will take placesimultaneously with the curing, however as the curing typically willproceed more slowly in highly diluted systems, drying will bepredominant in the initial phase of the drying and curing step and thecuring will be predominant in the later phase of this step.

After application of the binder to the fibres/particles, the drying andcuring is typically initiated by raising the temperature, e.g. bymoderate heating to a temperature in the range of 30-60° C., such as,but not generally required, in an inert or low-reactive atmosphere, e.g.a dehumidified atmosphere. Subsequent heating to 60-200° C., such as65-150° C., preferably 70-100° C., will lead to a rapid curing of thebinder, e.g. curing within 0.5-10 min. It is recommended that the watercontent should be less than about 50% by weight of the binder systembefore the temperature is increased to above around 100° C. (localboiling temperature for water), this particularly applies where thicklayers of binder is applied in order to avoid the formation ofimperfection in the product due to chock boiling of the water.

In a preferred embodiment where mineral fibres (mineral wool) are used,the binder composition is preferably sprayed onto the fibres just afterthe spinning of the glass or the stone melt, preferably already in thespinning chamber. The curing of the binder composition proceeds bybringing the sprayed fibres in an oven. It is advantageous to removesome of the water originating from the binder mixture before curing.This may, e.g., be done under reduced pressure or in a de-humidifiedenvironment or by slow heating up to curing temperature. The curingtemperature is normally in the range of 70-250° C., in particular in therange of 70-100° C. The sufficient curing time is normally in the rangeof 0.2-15 min. It is advantageous that the curing occurs in a CO₂depleted environment so as to avoid hygroscopic carbonates.

In the mineral fibre (mineral wool) embodiment, the raw materials forthe mineral fibres composition can be converted to a melt in theconventional manner, e.g. in a gas heated furnace or in an electricfurnace or in a shaft or cupola furnace. The melt can be converted intofibres in conventional manners, e.g. by the spinning cup process or bythe cascade rotor process such as described in WO 92/06047. Inparticular, the melt which is used for pouring onto the first rotor inorder to form the fibres can be any convenient vitreous melt suitablefor spinning by any spinner. Usually, such a melt is known as a stone,rock or slag melt. Man made vitreous fibres (MMVF) are made fromvitreous melts, e.g., formed from a number of molten mineral materialssuch as one or more of diabase, basalt, slag, limestone, dolomite,cement, clay, feldspar, sand or olivin. As mentioned above, the melt isformed by melting in a furnace the mineral raw materials so as to obtaina desired analysis. Examples of MMVF which are durable in use but whichhave been shown to be biologically soluble are, e.g. described in EP 0791 087 and EP 0 596 088.

The fibres can have any convenient fibre diameter and length. Generallythe average fibre diameter is below 10 μm, e.g. 5 μm. Usually, a mineralfibre product contains 1-15% by weight of binder, preferably 2-10% byweight. Usually, the binder is added to the fibres just afterfibersation of the melt.

Generally, the mineral fibre product is in the form of a slab, sheet orother shaped articles, e.g. pipes or pipe sections. A web of the thusformed materials can—before or after application of the binder—beconverted into any desired final product by conventional techniques,e.g., by direct collection or by cross-lapping, and subsequent ovencuring. The web may be formed into any conventional man-made vitreousfibre products such as heat insulation, fire protection, acousticinsulation and regulation, or horticultural growth media or fibres forreinforcement or as fillers. Examples hereof are sheets, e.g. sheetswhere the binder is unevenly distributed in volume of the sheet. In oneinteresting embodiment, at least a part of the outer surfaces of thesheet is treated with additional binder so as to provide modifiedproperties of the product or in order to provide further fire protectingproperties. This possibility also opens up for surface treatment ofmineral wool sheets with smoother, user-friendlier surfaces. Accordingto the possibility of modifying the hydrophobicity of the binder andthereby the product, it is also possible to modify the products so as toobtain either water repelling or water absorbing properties.

In general, the binder system of the present invention may be usedeither as replacement for or in combination with traditional phenolformaldehyde binders and mineral or silicone oils presently used inman-made vitreous fibre product. It is contemplated that a combinationof the binder system of the present invention can be mixed with aconventional phenol formaldehyde binder or sprayed on top of such phenolformaldehyde binders as a supplement or alternative to mineral orsilicone oils. Also, it is contemplated that the binder systems of thepresent invention may be mixed with mineral or silicone oils to provideexcellent properties for mineral wool products, e.g. dust free,non-brittle, water non-absorbing, fire retarding products.

The products according to the present invention may have a vast range ofapplications, not only within the field of heat and fire insulatingmaterials. Due to the hydrophobicity introduced with the binder systemincluding alkali metal organosiliconates, the products may be used ashydrophobic filters or as catalyst carriers or for filters comprisingcatalysts.

Another application for the products is as filling materials forcavities of aluminium profiles used as construction and buildingmaterials, e.g. for window frames. The advantage is that the product canbe based on inexpensive mineral fibre waste and cheap binder materialsand provide hydrophobic, water-non-absorbing materials.

A further possibility within the present invention is raw materials forthe production of mineral wool by mixing silica, alkali metal hydroxide,mineral wool waste and fly-ash.

The binder as such may be used as paint composition for concrete orbricks directly sprayable onto building material surfaces.

Furthermore, it is envisages that removal of water from a binder systemsolution/slurry, e.g. be dehumidifying the binder system to a watercontent of 20-30% by weight can provide a plastic material which can beformed (e.g. extruded) directly into interesting ceramic objects.

Porous Bodies Useful for Removing or Reducing the Content of OdorousSubstances From a Gas

A further aspect of the present invention relates to porous bodiesuseful for removing or reducing the content of odorous substances from agas. It should be noted that the definitions given in the following (upto the Examples section) relates to this aspect.

During the last decades a large research effort has been devoted to thefield of developing efficient adsorption agents. Nevertheless, the mostcommonly used adsorption agents are still activated carbon and silicagel and these adsorption agents are widely used within the chemicalindustries for removing toxic and odorous substances, for bleachingvarious oils, and for recovering of volatile organic solvents.

It is believed that two factors are responsible for an efficientadsorption of e.g. gas molecules to a solid surface.

First, the physical nature of the adsorption process is due to theso-called Van der Waal's forces which is dependent on the specificchemical nature of the adsorption agent and the adsorbent. Thus, theadsorption process is merely physical in nature and the adsorbedmolecules are held loosely to the solid surface. This, in turn, has theconsequence that the adsorbed molecules are easily “desorbed” e.g. bydisplacement or by applying heat to the system.

Secondly, the surface area of the adsorption agent plays a role in theefficiency of the adsorption process. Actually, the chemical nature ofthe surface is of minor significance and should be considered onlysecondary in relation to the major factor, i.e. the magnitude of thesurface area.

The internal surface area and with it the porosity of the adsorptionagent is therefore of major importance in developing new adsorptionagents. The large internal surface area in e.g. activated carbon is madeup by the micropore structure in the material.

If the chemical nature of the surface is regarded as playing a secondaryrole in adsorption, the adsorptive properties of a adsorption agent canbe attributed mainly to the surface area and hence the pore structure.It is apparent from pore size distribution data that the majorcontribution to surface area is located in pores of moleculardimensions, i.e. pores with a typical diameter in the range from 10-1000Å. Thus, a molecule will, due to steric effects, not readily penetrateinto a pore smaller than a certain critical diameter and will beexcluded from pores smaller than this.

The internal surface of activated carbon is usually in the range from500-1400 m²/g, i.e. the surface area may vary considerably depending onthe specific product and how this product is manufactured. Silica gel,on the other hand, usually has a smaller internal surface in the rangefrom 400-500 m²/g.

Activated carbon, however, suffers from the disadvantage that theproduct is very dusty, thus causing problems in the working environmentor when used in connection with electronic devices. Furthermore, formost practical applications of activated carbon as a filter material itis necessary to install filter bags in order to collect detached coaldust.

Thus, there is a need for materials which can be applied in adsorptionand filter systems without the disadvantages associated with the use ofactivated carbon.

It has now surprisingly been found that a new method for removingodorous substances from a gas, e.g. air, can be based on filtering thegas in question through a porous and easily produced material.

The material through which the gas is passed through possesses goodmechanical properties and due to its inorganic nature the material isinflammable. As will be apparent from the detailed description below,the material comprises mainly natural products which are very cheepindeed as well as environmental desirable. Another advantage is theextreme ease whereby such materials can be produced. Furthermore, thematerials are easily stored and transported as no problems arise due toe.g. microbiological growth, swelling caused by water absorption, etc.,and the materials are chemically inert and stable even at elevatedtemperatures.

Thus, the present invention relates to a method for removing or reducingthe content of odorous substances from a gas such as air, comprisingpassing the gas containing odorous substances through a filter of aproduct comprising a porous body or porous bodies produced from amaterial made from components comprising ultra-fine silica, water, andone or more components enabling porosity-conferring binding of thematerial.

The present invention also relates to a method for producing bodies foruse in the method for removing odorous substances from a gas such asair, comprising mixing ultra-fine silica, water, and one or morecomponents enabling porosity-conferring binding of the resultingmaterial, if-necessary removing water from the resulting mixture, andconverting the mixture to a body or bodies, the process being performedunder conditions resulting in a specific surface of the body or bodiesof at least 25 m²/g.

In the present context, the term “odorous substances” are intended tomean substances with a distinctive smell, which smell it is desired toremove or reduce for comfort purposes or even for health purposes, whichsmell may originate, e.g., from petrol and petrol stations, households,bodies, cosmetics, hospitals, kitchens, e.g. foods such as fats, cheese,garlic, onions, fish, etc., warehouses, welding, tobacco, desinfectants,automobile exhaust gas, car parks, airports, asphalt fumes, burnedflesh, burned food, citrus and other fruits, coal smoke, diesel fumes,essential oils, fertilisers, film processing, gasoline, incense,irritants, organic chemicals, packinghouses, paint and redecoratingodours, perfumes, pitches, poison gases, pollen, poultry, resins,rubber, sewer odours, slaughtering, smog, sour milk, toilets, stomi bagsvarnish, drains, etc., or combinations thereof.

The term “odorous substances” further comprises single molecules givingrise to a distinctive smell such as acetaldehyde, acetic acid, aceticanhydride, acetone, acetylene, acrolein, acrylic acid, acrylonitrile,amines, ammonia, amyl acetate, amyl alcohol, amyl ether, aniline,benzene, borane, bromine, butadiene, butane, butanone, butyl acetate,butyl alcohol, 2-butoxyethanol, butyl chloride, butyl ether, butylene,butyraldehyde, butyric acid, camphor, caprylic acid, carbolic acid,carbon disulfide, carbon dioxide, carbon monoxide, carbon tetrachloride,cellosolve, cellosolve acetate, chlorine, chlorobenzene,chlorobutadiene, chloroform, chloronitropropane, chloropicrin, creosote,cresols, croton-aldehyde, cyclohexane, cyclohexanol, cyclohexanone,cyclohexene, decane, dibromoethane, dichlorobenzene,dichlorodifluoromethane, dichloroethane, dichloroethylene, dichloroethylether, dichloromonofluormethane, dichloronitroethane, dichloropropane,dichlorotetrafluoroethane, diethylamine, diethyl ketone,dimethylaniline, dimethylsulphate, dioxane, dipropyl ketone, ethane,ether, ethyl acetate, ethyl acrylate, ethyl alcohol, ethyl amine, ethylbenzene, ethyl bromide, ethyl chloride, ethyl ether, ethyl formate,ethyl mercaptan, ethyl silicate, ethylene, ethylene chlorhydrin,ethylene dichloride, ethylene oxide, eucalyptole, fluortrichloromethane,formaldehyde, formic acid, heptane, heptylene, hexane, hexylene, hexyne,hydrogen, hydrogen bromide, hydrogenchloride, hydrogen cyanide, hydrogenfluoride, hydrogen iodide, hydrogen selenide, hydrogen sulfide, indole,iodine, iodoform, isophorone, isoprene, isopropyl acetate, isopropylalcohol, isopropyl chloride, isopropyl ether, kerosene, lactic acid,menthol, mercaptans, methane, methyl acetate, methyl acrylate, methylalcohol, methyl bromide, methyl butyl ketone, methyl cellosolve, methylcellosolve acetate, methyl chloride, methyl ether, methyl ethyl ketone,methyl formate, methyl isobutyl ketone, methyl mercaptan,methylcyclohexane, methylcyclohexanol, methylcyclohexanone, methylenechloride, monochlorobenzene, monofluorotrichlorometane, naphthalene,naphthziene, nicotine, nitric acid, nitro benzenes, nitroethane,nitrogen dioxide, nitroglycerine, nitromethane, nitropropane,nitrotoluene, nonane, octalene, octane, ozone, palmitic acid,paradichlorbenzene, pentane, pentanone, pentylene, pentyne,perchlorethylene, phenol, phosgene, propane, propionaldehyde, propionicacid, propyl acetate, propyl alcohol, propyl chloride, propyl ether,propyl mercaptan, propylene, propyne, putrescine, pyridine, styrenemonomer, sulphur dioxide, sulphur trioxide, sulphuric acid,tetrachlorethane, tetrachloroethylene, toluene, toluidine,trichloethylene, trichlorethane, turpentine, urea, uric acid, valericacid, valeric aldehyde, xylenes, etc., and combinations thereof.

Normally, the method of the invention will reduce the content of theodorous substances to at the most 50% of its initial concentration,preferably to at the most 30% or better at the most 20%, such as at themost 10% or less. The reduction aimed at is often a substantiallycomplete removal of the odorous substances.

The product for removing odorous substances according to the inventioncomprises a porous body or bodies produced from a material made fromcomponents comprising ultrafine silica, water, one or more componentsenabling porosity-conferring binding of the material, and optionallyfiller bodies, porosity-enhancing bodies, and non-ionic, cationic,and/or anionic surfactants. The product may consist solely of the porousbody or bodies, or the product may contain components in addition to thebodies, e.g., a structure, such as a grid or network or a component,such as an adhesive, keeping several bodies together in a random orordered configuration.

In the present context the term “ultra-fine silica” is intended todesignate SiO₂-rich particles having a specific surface of about 5 m²/gto 200 m²/g, especially about 10 m²/g to 50 m²/g. Such a product isproduced as a by-product in the production of silicium metal inelectrical furnaces and comprises particles in a particle-size rangefrom about 50 Å to about 0.75 μm, typically in the range from about 200Å to about 0.75 μm.

The porous bodies are then typically filled into cartridges by methodsknown to the person skilled in the art, e.g. by methods usually employedwhen filling active carbon into cartridges.

The component enabling porosity-conferring binding of the material fromwhich the bodies are made so as to result in porous bodies may be adispersed (in the form of particles or droplets) or dissolved reactantwhich is capable of reaction with the ultra-fine silica to result in asolid microstructure which is porous. The porous microstructure may beof a generally “sintered” character, where discernable particles of theultra-fine silica and/or of the component in question are bound to eachother in menisci of a solidified (precipitated) material, normally amaterial formed by the reaction between the ultra-fine silica and thecomponent in question, or the porous microstructure may be a generallyamorphous material or generally crystalline microstructure resultingfrom a reaction between the ultra-fine silica and the component in theaqueous phase and precipitation of the amorphous material.

Interesting examples of components enabling porosity-conferring bindingare bases e.g. alkali or alkaline earth metal hydroxides, such as sodiumhydroxide, potassium hydroxide, magnesium hydroxide, and calciumhydroxide, alkali or alkaline earth metal silicates, aluminiumsilicates, iron (in the oxidation state II or II) silicates, andmixtures thereof, alkali or alkaline earth metal pyrosilicates,aluminium pyrosilicates, iron (in the oxidation state II or II)pyrosilicates, and mixtures thereof, alkali or alkaline earth metalcarbonates, alkali or alkaline earth metal bicarbonates, alkali oralkaline earth metal phosphates, alkali or alkaline earth metalpyrophosphates, perlite, ammonia, and organic amines, such as primary,secondary, and tertiary amines, e.g., methylamine, dimethylamine,trimethylamine, ethylamine, diethylamine, triethylamine, and anilines,such as aniline, methylaniline, dimethylaniline, etc., and cements, suchas basic Portland cement, rapid Portland cement, high early strengthPortland cement, sulphate resistant cement, low-alkali cement, low heatcement, white Portland cement, Portland blast furnace cement, Portlandpozzolana cement, Hasle cement, ultra Cement and aluminate cement (highalumina cement) or combinations thereof.

Preferably the base is selected from cements, perlite, and alkali oralkaline earth metal hydroxides, especially calcium hydroxide.

Without being bound by a specific theory, it is believed that thecomponents enabling porosity-conferring binding, such as bases, willoften be components which react chemically with part of the silica,thereby creating “cavities” in the silica framework which in turnincrease the surface area and with it the porosity of the resultingmaterial.

In the present context the term “fibres” is intended to mean any fibreswithin the groups of natural inorganic fibres, synthetic inorganicfibres, natural organic fibres, synthetic organic fibres, and metallicfibres, or mixtures thereof, preferably inorganic or organic fibres ormixtures thereof. Furthermore, the term “fibres” is intended to covermonofilaments, split fibres, and stable fibres of any cross section.Thus, the term also comprises bands, granules, needles, whiskers, andstrips. The fibres may or may not have been surface treated or coated.

Thus, in an interesting embodiment of the method according to theinvention, the material through which the odorous substances are passedthrough also comprises one or more filler bodies such as fibres andparticles. Preferred examples of fibres are silicon-containing fibres,metal fibres, oxide fibres, carbon fibres, glass fibres including microglass fibres, Rockwool fibres, processed mineral fibres from mineralwool, volcanic rock fibres, wollastonite fibres, montmorillonite fibres,tobermorite fibres, biotite fibres, atapulgite fibres, calcined bauxitefibres, aromatic polyamide fibres, aromatic polyester fibres, aromaticpolyimide fibres, cellulose fibres, cotton fibres, flax fibres, rubberfibres and fibres of derivatives of rubber, polyolefin fibres includingpolyethylene and polypropylene fibres, polyacetylene fibres, polyesterfibres, acrylic fibres and modified acrylic fibres, acrylonitrilefibres, elastomeric fibres, protein fibres, alginate fibres,poly(ethylene terephthalate) fibres, polyvinyl alcohol fibres, aliphaticpolyamide fibres, polyvinylchloride fibres, polyurethane fibres, vinylpolymeric fibres, and viscose fibres, modified by any chemical orphysical processes, and any mixtures thereof.

Preferred fibres are micro glass fibres, Rockwool®) fibres, wood fibres,plant fibres, polypropylene fibres and polyethylene fibres.

In a particular interesting embodiment of the invention the materialthrough which the odorous substances are passed through comprises one ormore filler bodies selected from cellulose fibres. Specific examples ofcellulose fibres are for example cotton fibres, wheat fibres, agarfibres, flax fibres, pea fibres, barley firbres, oat fibres, cocoafibres, coffee fibres, orange fibres, citrus fibres, apple fibres,tomato fibres, carrot fibres, soya fibres and acacia fibres. Thepresently most preferred cellulose fibres are fibres selected fromexample cotton fibres, wheat fibres and agar fibres.

In another interesting embodiment of the invention the cellulose fibresmay be obtained from a paper source such as chopped newspapers, choppedvirgin paper or paper which has been de-fibrated by means of a hammermill.

As will be apparent from the examples provided herein chopped paper maybe prepared by cross-cutting the paper in a shredding machine.Preferably the cross-cut paper has a length of 0.1 to 1 mm and a widthof 0.4 to 0.9 mm.

It should be understood that the amount of cellulose fibres present inthe porous material constitutes a compromise; the amount of cellulosefibres should one the one hand be as large as possible in order toincrease the absorption properties of the porous material but, on theother hand, the amount of cellulose fibres should be as low as possiblein order to prevent or reduce the inflammability of the porous material.It has been found by the present inventor that in order to obtainsatisfactory absorption properties, the amount of cellulose fibres inthe porous material will generally be in the interval from 4% to 75% byweight, preferably 10% to about 50% by weight, in particular from 15% toabout 35% by weight.

It has been found, however, that it is possible to obtain satisfactoryabsorption properties of the porous material even when the amount ofcellulose fibres are very low, i.e. in the range from 4% to 10% byweight, such as about 7% by weight. As explained above, the advantage ofusing such low amounts of cellulose fibres is that the porous materialwill not be inflammable.

Examples of suitable particles are particles which tend to be insolubleunder the conditions prevailing during the reaction between theultra-fine silica and the porosity-conferring component, e.g., fine (butnot ultra-fine and not reactive) silica particles such as ground quartsand silica gel particles, other ground mineral particles such as heavyspar, bentonite, diatomite, dolomite, feldspar, kaolin, spherical andhollow particles, carbon particles, talc, mica, vermiculite, kiselguhraluminium silicate, chalk, and fly ash etc. Especially interestingfiller particles are porosity-enhancing bodies such as mica, chalk,vermiculite, or combinations thereof.

In another interesting embodiment of the method of the invention, thematerial from which the porous bodies are made may comprise one or moreorganic components such as straw, cellulose fibres, polymer fibres,textile fibres, cotton fibres, flax fibres, pulverised plant shellsetc., so that when the porous bodies made from the material areincinerated, typically at a temperature around 700° C. in an inertatmosphere, the organic components will carbonise, i.e. the final porousbodies will be carrying elemental carbon on surfaces thereof, so as toestablish an economical “supported” active carbon.

Furthermore, in some cases it may be advantageous to add surfactants tothe reaction mixture. Thus, addition of non-ionic, anionic, and cationicsurfactants to the reaction mixture may provide a more smooth processing(e.g. extrusion) of the material. However, the addition of surfactantsto the reaction mixture is not presently preferred.

Examples of suitable surfactants are e.g. anionic surfactants such asderivatives of fatty acids wherein the negative charge is provided by afree carboxyl group, a sulphonate group, or a phosphate group, and suchanionic surfactants commonly used in rinse aids; non-ionic surfactantssuch as esters or partial esters of fatty acids with an aliphaticpolyhydric alcohol such as e.g. ethylene glycol, glycerol, sorbitol,etc., and the polyoxyethylene and polyoxypropylene derivatives of theseesters, and such non-ionic surfactants commonly used in rinse aids;cationic surfactants such as derivatives of fatty acids, wherein thepositive charge is provided by one or more quaternary ammonium groups,and such cationic surfactants commonly used in detergents. Fatty acidstypically contain from 6 to 22 carbon atoms; examples are caproic,octanoic, lauric, palmitic, stearic, linoleic, linolenic, olesteric, andoleic acid, etc.

Various accelerators and retarders may optionally be added to thereaction mixture. Examples of suitable accelerators are e.g calciumformate, calcium chloride, alkali metal nitrates, and ammonium nitrates.Examples of suitable retarders are polyhydroxycabocide, and alkali oralkaline earth metal phosphates.

The porous materials should preferably have a bulk density in the rangefrom about 300 kg/m³ to about 700 kg/m³. It has been found that porousmaterials having a bulk density below 300 kg/m³ is too brittle and,consequently, not suitable for the purposes of the present invention.Preferably, the porous materials should have a bulk density which isbelow that of carbon, i.e. a the porous materials should preferably havea bulk density below 525-550 kg/m³. It is contemplated that particularlyinteresting porous materials will have a bulk density in the range from400 to 450 kg/m³.

As will be understood from the examples provided herein, the porousbodies through which the odorous substances are passed are easilyproduced by a batch process. However, due to the simple production, thematerial through which the odorous substances are passed through mayalso be produced in a continuous process such as illustrated in FIG. 1below.

As will be understood from the examples provided herein, one way ofproducing the material from which the porous bodies are made is bymixing ultra-fine silica, water and the component enablingporosity-conferring binding of the resulting material while stirringuntil a workable powder substance is formed, or at the most for 30 min.,preferably for at the most 15 min.

When applying a strong base (such as e.g. lime water) the initial pH inthe aqueous phase is usually at least 10, such as at least 10.5,preferably at least 11. In this specific case the reaction is preferablycontinued until the pH in the aqueous phase is at the most 9, or at themost a pH which will secure a specific surface area of at least 25 m²/g,e.g. at least 50 m²/g, such as at least 100 m²/g, preferably at least200 m²/g, even more preferably at least 300 m²/g, in particular at least400 m²/g, especially at least 500 m²/g, such as at least 600 m²/g.

Without being bound by a specific theory, it is believed that theabove-mentioned pH-drop is provided by the excess of silica present inthe reaction mixture. It is believed that the decrease in the pH is ofoutmost importance, and therefore, in another embodiment, wherein silicais not present in excess, the pH-drop may be provided by addition ofacidic components to the reaction mixture, such as silica, mica,inorganic acids, such as hydrochloric acid, hydrobromic acid, sulphuricacid, nitric acid, etc. and organic acids, such as acetic acid,propionic acid, etc. and such acids as known to a person skilled in theart.

It will be understood from the examples provided herein that thematerial, while still shapeable, that is, before hardening, is easilyconverted into almost any shape desirable. Thus, the material is easilyconverted into a body or bodies of sheets, plates, firm and brittlepellets, bars, sticks, bricks, pipes, tubes, tapes, noodles, shells,fibre-like products, and spaghetti-like products etc., by means ofmethods known to a person skilled in the art, such as extrusion,casting, pressing, moulding, injection moulding, etc., optionallycombined with or followed by evaporation and/or heating. An oftenpreferred method is to extrude the material, while extrudable, into amultitude of strings of a cross-sectional dimension, such as diameter,of, e.g. 1-5 mm and chop the strings in short lengths, typically 3-30 mmsuch as 5-12 mm, to form pellets which are then hardened, typically bydrying.

In a preferred embodiment the material is then stored in an atmosphereof at least 75% relative humidity, such as at least 80% relativehumidity, preferably at least 85% relative humidity, even morepreferably at least 90% relative humidity, such as at least 99% relativehumidity, in order to pre-harden the material. Optionally, the materialis then subjected to a final drying step in order to remove excesswater.

In general, materials which exhibit a neutral pH when suspended in waterare preferred. Thus, in a preferred embodiment the material (with orwithout storage under humid conditions) has a pH in the range of 5 to 9,such as in the range from 5.5 to 8.5, preferably in the range from 6 to8, even more preferably in the range from 6.5 to 7.5, e.g. around 7,based on a 4 mg ground sample of the material suspended in 25 mldemineralised water.

Macrostructures comprising several of the porous bodies, e.g., severalpellets, may be produced from the dry pellets by “gluing” them togetherby means of an organic or inorganic (such as a cement slurry) in amanner known per se. In a particular embodiment, the same reactionmixture from which the bodies may be made by extrusion and chopping maybe used in itself as an inorganic adhesive, optionally after dilution.

However, it is also possible to obtain the bodies as minute particlesconstituting a free-flowing powder by removing excess solvent waterafter the reaction has completed. Thus, instead of the above-mentionedprocessing (casting, extrusion, etc.) the excess water can, ifnecessary, be removed by filtration, evaporation, suction, autoclaving,etc., and the resulting material comprising fine particles can be driedby means of any standard procedure known to a person skilled in the art,including air-drying at ambient temperature and pressure.

It is envisaged that when producing the porous bodies in a continuousindustrial process, it may be advantageous to supply at least part ofthe water as steam due to a decrease in the sliding friction of thereaction mixture.

In another interesting embodiment of the invention the the material fromwhich the porous bodies are made is produced by a slightly modifiedprocess compared to the process described above. This process isparticular suitable when the porous bodies comprise fibres, such ascellulose fibres.

Thus, by employing the above-mentioned slightly modified process theextrusion step may be avoided. In general, the slightly modified methodcomprises the following steps: The fibres are added to a silica slurry(preferably comprising from about 30% to 70% by weight of silica,preferably around 50% by weight) while stirring and, in the case ofcellulose fibres, while blending the mixture in order to de-fibrate (orpartly de-fibrate) the cellulose fibres until a thixotropic mass(viscous paste) is obtained. Stirring is then continued until a“dough-like” material is formed. If only a small amount of fibres (i.e.less than about 10-20% by weight) is employed it will normally benecessary to add perlite (typically from 10% to 70% by weight) in orderto obtain the above-mentioned “dough-like” structure of the material.

After the “dough-like” structure is obtained a base such as Ca(OH)₂ or acement is added under vigorous stirring whereby a workable mass will beobtained. By continuing stirring small grains are formed which will growinto small pellets if stirring is continued. Thus, it should beunderstood that the dimension of the pellets produced may be controlledby the stirring time after addition of the base (typically a cement).The diameter of the pellets produced will typically be in the range fromabout 1 to 8 mm. Preferably the materials produced as described aboveshould be hardened by methods known to the person skilled in the art,such as hydraulic hardening for 28 days without draining the product;autoclaving; or hydraulic hardening in a closed, insulated box.Optionally, the material is then subjected to a final drying step inorder to remove excess water.

The above method according to the invention has numerous possibleapplications. Thus, one application of the method according to theinvention is the use of the method in ventilation systems e.g. such asin car parks, households, airports, hospital kitchens, garages, petrolstations, factories, warehouses, department stores, toilets, meetingrooms, hairdressing saloons, hotels, etc.

Another application within the scope of the invention is the use of themethod in masks for adsorbing organic or inorganic chemicals whichoriginate from e.g. paint, spray-painting, solvents, etc.

A third application within the scope of the invention is the use of themethod in general environmental protection by adsorbing odorous and/ortoxic substances from chimney smoke in industrial plants, such aschemical plants, power stations, etc.

A fourth application within the scope of the invention relates to thepossibility of incorporating catalytically active materials into thepores of the material. Thus, the porous material may perform thefunction of a carrier.

Due to the general adsorption properties of the porous bodies, it iscontemplated that they may also be ideally useful for removing wastesubstances from an aqueous medium.

Thus, the present invention also relates to a method for removing orreducing the concentration of waste substances from an aqueous medium,comprising passing the aqueous medium containing waste substancesthrough a filter of a product comprising a porous body or porous bodiesproduced from a material made from components comprising ultra-finesilica, water, and a component enabling porosity-conferring binding ofthe material.

In the present context the term “waste substances” is intended to meanundesirable chemical substances commonly found in e.g. waste water,drinking water, ground water, etc.

Examples of waste substances are e.g. inorganic substances such aschromium, iron, cobalt, nickel, copper, zinc, cadmium, mercury,aluminium, lead, arsenic, etc. in any commonly found oxidation step,pesticides e.g. such as hexachlorocyclohexane, hexachlorobenzene,pentachlorophenol, 2,4,5-trichlorophenoxy acetate, hexachlorophen,dioxin, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), polychlorinatedbiphenyl (PCB), dichlorodiphenyltrichlorethane (DDT), etc., andbreakdown products thereof, polyaromatic hydrocarbons comprising from10-22 carbon atoms such as naphthalene, anthracene, phenanthrene,dibenz[a,h]anthracene, benzo[a]pyrene, 7,12-dimethyl-benz[a]anthracene,etc., and smaller organic molecules commonly found in e.g. ground waterand waste water such as acetaldehyde, acetic acid, acetic anhydride,acetone, acetylene, acrolein, acrylic acid, acrylonitrile, amines, amylacetate, amyl alcohol, amyl ether, aniline, benzene, borane, butanone,butyl acetate, butyl alcohol, 2-butoxyethanol, butyl chloride, butylether, butylene, butyraldehyde, butyric acid, camphor, caprylic acid,carbolic acid, carbon tetrachloride, cellosolve, cellosolve acetate,chlorobenzene, chlorobutadiene, chloroform, chloronitropropane,chloropicrin, creosote, cresols, crotonaldehyde, cyclo-hexane,cyclohexanol, cyclohexanone, cyclohexene, decane, dibromoethane,dichloro-benzene, dichlorodifluoromethane, dichloroethane,dichloroethylene, dichloroethyl ether, dichloromonofluormethane,dichloronitroethane, dichloropropane, dichlorotetrafluoroethane,diethylamine, diethyl ketone, dimethylaniline, dimethylsulphate,dioxane, dipropyl ketone, ethers, ethyl acetate, ethyl acrylate, ethylalcohol, ethyl amine, ethyl benzene, ethyl bromide, ethyl chloride,ethyl ether, ethyl formate, ethyl mercaptan, ethyl silicate, ethylenechlorhydrin, ethylene dichloride, ethylene oxide, eucalyptole,fluortrichloromethane, formaldehyde, formic acid, heptane, heptylene,hexane, hexylene, hexyne, cyanide, indole, iodoform, isophorone,isoprene, isopropyl acetate, isopropyl alcohol, isopropyl chloride,isopropyl ether, kerosene, lactic acid, menthol, mercaptans, methylacetate, methyl acrylate, methyl alcohol, methyl bromide, methyl butylketone, methyl cellosolve, methyl cellosolve acetate, methyl chloride,methyl ether, methyl ethyl ketone, methyl formate, methyl isobutylketone, methyl mercaptan, methylcyclohexane, methylcyclohexanol,methylcyclohexanone, methylene chloride, monochlorobenzene,mono-fluorotrichlorometane, naphthalene, naphthziene, nicotine, nitrobenzenes, nitroethane, nitroglycerine, nitrotoluene, nonane, octalene,octane, palmitic acid, paradichlorbenzene, pentane, pentanone,pentylene, pentyne, perchlorethylene, phenol, propionaldehyde, propionicacid, propyl acetate, propyl alcohol, propyl chloride, propyl ether,propyl mercaptan, putrescine, pyridine, styrene monomer,tetrachlorethane, tetrachloroethylene, toluene, toluidine,trichloethylene, trichlorethane, turpentine, urea, uric acid, valericacid, valeric aldehyde, xylenes, etc., and combinations thereof.

Also in this connection, the method of the invention is preferablyadapted to reduce the content of the odorous substances to at the most50% of its initial concentration, preferably to at the most 30% orbetter at the most 20%, such as at the most 10% or less. The reductionaimed at is often a substantially complete removal of the wastesubstances.

A further important use of the principles of the invention is a methodfor thixotroping bitumen, in particular bitumen used in roadconstruction, in which method porous bodies of the type characterisedherein are added to hot bitumen, and the bodies (and/or fragmentsthereof resulting from full or partial disintegration of the bodies) tobe distributed in the bitumen. In this manner, the bitumen can be madesufficiently thixotropic to substantially avoid sedimentation of coarseaggregate such as gravel or stones in the road construction. As anexample, runways in airports are preferably made with a highconcentration of coarse aggregate part of which is to remain in thesurface of the resulting runway to ensure sufficient friction;sedimentation of the aggregate would tend to remove aggregate from thesurface. Presently, cellulose fibres are often used to confer thixotropyto bitumen to avoid sedimentation of coarse aggregate. The bodies usedaccording to the invention have the advantage that they are inorganicand can be made “crunchy” and easy to distribute as such orpredominantly in more or less disintegrated form (the disintegrationbeing a result of agitation and attrition between particles ofaggregate) to result in a high resistance to coarse aggregatesedimentation.

In a preferred embodiment the porous bodies are added to the coarseaggregate, e.g. dried warm stones and filler materials after which theresulting composition is mixed whereby the porous bodies are crushed.The hot low-viscosity bitumen is then added to the resulting coarseaggregate/porous body mixture so that the final concentration of theporous bodies in the asphalt is from 0.1-1% by weight, in particular0.2-0.5% by weight, calculated on the bitumen. The temperature of thebitumen at the time of addition is normally in the range of 160-200° C.,in particular 170-180° C. Typically, the bitumen and the coarseaggregate/porous body mixture is mixed from a few seconds to 5 min,preferably from 5 seconds to 1 min, even more preferably from 10 secondsto 30 seconds, such as from 10 seconds to 20 seconds.

A particularly suitable type of bodies for this use are bodies made fromultra-fine silica present in an amount from 10 to 60% by weight,preferably from 20 to 50% by weight, such as from 30 to 40% by weight,water, present in an amount from 5 to 50% by weight, preferably from 10to 40% by weight, such as from 20 to 30% by weight, and perlite, presentin an amount from 10 to 60% by weight, preferably from 20 to 50% byweight, such as from 30 to 40% by weight, as the sole or maincomponents.

The bodies are normally added to the bitumen in an amount of 0.1-1% byweight, in particular 0.2-0.5% by weight, calculated on the bitumen. Thetemperature of the bitumen at the time of addition of the bodies isnormally in the range of 160-200° C., in particular 170-180° C.

A further aspect of the invention relates to a method for producingfilter paper or filter cardboard from a cellulose fibre-containing pulp,comprising flocculating the pulp by adding ultra-fine silica to the pulpand reacting it in situ with a dissolved base, such as e.g. lime wateror a polyelectrolyte.

As the porous materials are new the present invention also relates to aproduct comprising a porous body or porous bodies comprising silica,preferably ultra-fine silica and one or more bases.

In an interesting embodiment of the invention the product comprising theporous body or the porous bodies comprises at least 35% by weight ofultra-fine silica (calculated on the total weight of the product),preferably at least 40% by weight, such as at least 45% by weight, inparticular at least 50% by weight and one or more bases.

The base (or bases) is preferably selected from the group consisting ofCa(OH)₂, cement and perlite and mixtures thereof.

Thus, in another interesting embodiment of the present invention theproduct comprising the porous body or the porous bodies comprises atleast 35% by weight of ultra-fine silica (calculated on the total weightof the product), preferably at least 40% by weight, such as at least 45%by weight, in particular at least 50% by weight, perlite and/or cement.In a particular interesting embodiment of the invention the productcomprising the porous body or the porous bodies further comprises afiller body selected from fibres and particles. Preferably the fibresare selected from cellulose fibres and/or mineral fibres. These fibresare typically present in an amount from 4% to 75% by weight, preferably10% to about 50% by weight, in particular from 15% to about 35% byweight (calculated on the total weight of the product).

Description of FIG. 1:

Various raw materials (loose silica, densified silica, silica slurry,perlite, cements, wood flour, ground straw, etc.) are stored in silos 1to 9. Depending on which particular product one wants to produce, theraw materials are dosed by opening the relevant silos 1 to 9. The rawmaterials are transported to the mixing machine 10 by means of the feedscrew 11 driven by the engine 12. Raw chemicals are stored in tank 13(surfactants), 14 (surfactants), and 15 (calcium chloride or anotheraccelerator or retarder). Depending on which particular product onewants to produce, the raw chemicals are dosed by opening the relevanttanks 13 to 15. Water is added through the pipe 16 to the raw chemicals(if raw chemicals are employed) and the resulting mixture is mixed inthe pre-mixer 17 after which the resulting mixture by means of the pump18 is driven through the nozzles 19 and added to the raw materials inthe mixing machine 10. The resulting “paste” or powder is thentransported to a storage tank 20 by means of an elevator 21 wherein the“paste” or powder is stored for at the most 15 minuttes, optionally fora shorter or longer period dependent on whether an accelerator orretarder is present. The “paste” or powder is then transported to thepre-press machine 22 by means of the feed screw 23 driven by the engine24. After the pressing procedure, the material is granulated in agranulation machine 25, and then extruded in an extruder 26 optionallyconnected to a steam supply 27. The porous material is extruded intopellets with a diameter typically in the range from 2 to 5 mm, and isthen via the conveyor belt 28 transported to a drying (or cooling) room29 after which the porous material is passed through the sieve 30 andfinally packed in bags 31 optionally equipped with an inner surface ofplastic so that the porous material may continue the hardening processwhile stored.

EXAMPLES

All values are in grams (g) unless otherwise specified. % is percent byweight unless otherwise stated.

Silica slurry was obtained from Elkem Materials, Norway (ElkemMicrosilica® slurry). The concentration of the slurry was 50% silica byweight.

Potassium methyl siliconate as a 42% aqueous solution (Wacker BS-15) wasobtained from Wacker Chemie GmbH, Germay.

Potassium hydroxide pellets were obtained from Bie & Bemtsen A/S,Denmark.

Sodium hydroxide pellets (Afløbsrens) were obtained from the grocerystore.

Rockwool® Hulrumsfyid (mineral wool) and Glasuld® Hulrumsfyld (glasswool) from Ledreborg Tømmerhandel, Roskilde, Denmark.

Loose silica was obtained from Elkem Materials, Norway (ElkemMicrosilica®).

Densified silica was obtained from Elkem Materials, Norway.

Sand-lime mortar was obtained from Dansk SystemMørtel A/S, Denmark.

Soda lye (27%) and soda water glass was obtained from Borup Kemi,Denmark.

Basic, rapid, ultra and white cements were obtained from AalborgPortland, Denmark, and Hasle cement was obtained from HasleRefractories, Denmark.

Perlite, with a mean particle size less than 14 μm, and less than 7 μmwas obtained from Nordisk Perlite, Denmark (type 50 and type 180,respectively).

Wood flour (beech wood flour T 100) was obtained from JunckersIndustries, Denmark.

Carboxy methyl cellulose (CMC powder, Arabin cellulose tapetklister) wasobtained from De Carlske Fabrikker, Denmark.

Chopped paper (having a dimension of 9 mm×0.7 mm) was prepared fromnewspapers (having a weight per m² of less than 48) by cross-cutting thenewspapers in a shredding machine (cross-cut).

Wheat fibres (Wheat fibre ID 48) was obtained from Cergy Pontoise Cedex,France. Cotton fibres (Vegetable fibre isolate ID 99) was obtained fromCergy Pontoise Cedex, France.

Food Agar (Thixotropic Quick Soluble Agar Dl 00) was obtained fromSetexam, Usine El Assam, 14000 Kenitra, Morocco.

Non-ionic and cationic surfactants in the form of detergent (Vel UltraOpvaskemiddel) was obtained from Colgate-Palmolive A/S, Denmark.According to the declaration of contents 30 the product contains morethan 30% of anionic surfactants, and less than 5% of non-ionicsurfactants.

Cationic surfactants in the form of rinse aid (Net-Op) was obtained fromDansk Supermarked Indkøb A/S, Denmark. According to the declaration ofcontents the product contains 15-30% of cationic surfactants.

Activated carbon (type 207 E3, 3 mm pellets and type 207 E4, 4 mmpellets) was obtained from Sutcliffe Speakman Carbons Ltd, Lancashire,England. This product was employed in the “Oil absorption test”.

Activated carbon (as a powder) was obtained from Sutcliffe SpeakmanCarbons Ltd, Lancashire, England. This product was employed in theporous materials.

Ground straw with a length of less than 5 μm was prepared in a hammermill.

Polymer particles (Keydime S) were obtained from Eka Nobel Industries,Sweden.

The high-speed mixer used was a domestic handheld mixer (BraunMultiquick MR405, 4185).

The (low-speed) mixer used was a domestic mixer (Kenwood Major ClassicKM800).

The microwave oven used was a domestic microwave oven (Gorenje Kombi 971Kombiovn—effect 950W). The setting was 80% of the maximum effect unlessotherwise stated.

A dehumidified used to reduce the relative humidity in the laboratorywas a Westtherm Model DH 3212.

Binder Systems and Products Comprising the Same

General Procedure for the Preparation of the Binder Systems A-C, I-L andV-Y

The silica in the form of a 50% (w/w) slurry was added to a container.The potassium methyl siliconate (as a solution) and/or alkali metalhydroxide and additional water was added while stirring vigorously witha high-speed mixer (full power) for 10-15 min (applied energy wasestimated to around 0.04 kWh/kg). For the binders, which all included analkaline organosiliconate, a marked increase in the viscosity was firstobserved, however after approximately 10 min of mixing, the viscositydecreased to a creamy liquid. Without being bound to any specifictheory, it is believed that this was due to the fact that the mixturewas not optimally mixed in the beginning and that reaction between thesilica and the alkaline siliconate had only taken place to a lesserextent. (It was important that the mixing was performed at high speed asthe mixture of the silica and the alkaline siliconate would otherwiseresult in a partially gel-like product which was unsatisfactory for useas a binder.)

The constitution of each of the binder systems A-C, I-L and V-Y is shownin Table I. TABLE I Binder No. A B C I J K L Silica slurry (50%) 500 500500 500 500 500 500 Potassium methyl 25 50 100 siliconate (42%)Additional water 25 50 100 KOH solution: KOH (solid) 15 25 Water 250 250NaOH solution: NaOH (solid) 15 25 Water 250 250 Binder No. V X Z Silicaslurry (50%) 500 500 500 Potassium methyl 10 10 10 siliconate (42%)Additional water 10 10 10 KOH solution: KOH (solid) 15 10 Water 250 175NaOH solution: NaOH (solid) 15 5 Additional Water 250 75

All of the binders A-C, I-L and V-Z had a viscosity corresponding to acreamy liquid.

Due to the increase in the amount of organosiliconate used, thehydrophobicity appeared to increase from binder A to C. This wasobserved as an increase in contact angle when a drop of water was addedto a mineral wool product (a mineral wool material (Rockwool®Hulrumsfyld) onto which the water-based binder mixture was previouslyapplied by brush, dried at around 50° C. and cured in a microwave oven).For binder A-C the contact angle was estimated to 90-110 with thehighest contact angle for C.

The binders I-L were prepared as above and were estimated to have thesame viscosity as for A-C. After storage for 1-50 days some gellingoccurred and the viscosity consequently dramatically increased. The pHafter storage was around 10-13. Materials wherein those binders wereused appeared to be slightly more brittle than the one where either asiliconate or a mixture of a siliconate and base were used.

The binders V-Z showed properties in consistency with the ones mentionedabove.

General Procedure for Application of the Binder Component to Fibre orParticle Materials

The binder mixture was either brushed onto the material or the materialwas dipped in the binder mixture and pressed to remove excess binder(mineral wool) or mixed with the mineral particle material (sand). Thematerials with the binder were dried by evaporation of 80% of the excesswater (estimated) by heating at around 50° C. and were cured in adomestic microwave oven (setting 70-80% intensity) for 5-8 minutes. Thecompositions are shown in Table II. TABLE II Experiment No. D E F G H MN Binder: A 50 B 50 225 200 25 C 50 I 25 J 50 Rockwool ® 150 HulrumsfyldSand 350 350 350 350 350 Perlite < 2 mm 100 Experiment No. O P Q R S T UBinder: B 100 100 100 100 100 25 I 125 J 100 100 K 125 25 L 100 50Rockwool ® 150 150 Hulrumsfyld Sand 350 350 Perlite < 2 mm 100 100 Woodcellulose 100

Experiments D-F resembles the binding between native vitreous fibres(non-surface treated) and the binder system. Even at a content of lessthan around 5% siliconate, the binding strength was satisfactory.

Experiment G shows the combination of a surface-treated vitreous fibreproduct and the binder. Regardless of the already surface-modifiedfibres, the binding strength between the binder system and the fibreswas considered satisfactory.

The experiments M and N is a comparison between a binder system preparedwith a base but without siliconate and a binder system with a base and asiliconate. The latter example provides a higher degree ofhydrophobicity and furthermore a less “brittle” product.

The experiments O to S show various advantageous binder systemscomprising a siliconate as well as a base.

The experiments T and U show comparative examples of a binder systemcomprising a a base exclusively and a siliconate and a base. The latterbinder system showed a higher hydrophobicity when estimating the contactangle of a water drop (see above).

Preparation of Light, Porous Products

The products 91-100 relates to castings of micro-porous pellet productsprepared exclusively from silica, cement and water. The aim of theexperiment was to prepare a light, cheap, non-flammable, robust, castinginsulating material from these materials and optionally mineral woolfibres as reinforcement, such material optionally being renderedhydrophobic by addition of siliconate. The products were prepared asfollows: a cement slurry was prepared from ultra-fine cement and water(the finer cement the more satisfactory slurry) by vigorously mixingwith a high speed mixer for 8 min (unless otherwise stated). The silicaslurry and the cement slurry is then mixed vigorously for another 8 min.(unless otherwise stated) resulting in a relatively rigid egg-whitefoamy masse which cures at room temperature as concrete or porousconcrete. Accelerators and retarders may be added. This very lightfoamy, porous product is remarkably in that essentially no shrinkingoccurs—even without additives. The important feature is to have thecement to react as a base to gel the silica slurry. This is effectedunder vigorous mixing. The more water added to the mixture, the lowerthe strength of the cured product. The most promising relation betweensilica and cement is 75:25-50:50 by weight.

Products 101-106 are prepared essentially as above, where thesilica:cement ratio is 80:20-68:32, but with Rockwool® Hulrumsfyid as amineral fibre. The aim was to lower the density without increasing thequality (strength) of the pellets. Lower densities were obtained by alsoa slight decrease in strength.

Products 107-111 relates to pellet products with Glass wool as mineralfibre. The water content and the cement type is varied and some productscomprise active carbon. Having about the same densities as the previousproducts in this series, the best product (homogenity) was obtained withGlass wool. TABLE III Product No. 91 92 93 94 95 96 97 98 Silica 10001000 1000 1000 1000 1000 1000 1000 slurry (50%) Additional 500 400 250200 400 400 400 400 water Rapid 250 200 125 100 75 250 200 125 cement pHafter 12 11-12 10 9-10 9 12 11-12 10 28 days Product No. 99 100 101 102103 104 105 106 Silica slurry 1000 1000 1000 1000 1000 1000 1000 1000(50%) Additional 400 400 400 400 400 1200 1200 1200 water Rockwool ® 500400 600 1200 800 800 Hulrumsfyld Rapid cement 100 75 100 100 100 100 160100 pH after 28 9-10 9 days Mixing time, 10 8 9 10 12 10 min. Bulkdensity 339 325 333 334 256 273 kg/m³ Product No. 107 108 109 110 111Silica slurry (50%) 1200 1200 1200 1200 1200 Additional water 400 500500 500 500 Carbon powder 120 300 300 850 m²/g Rockwool ® 500 400 600Hulrumsfyld Glasuld ® 480 480 480 480 480 Hulrumsfyld Rapid cement 120120 120 120 Ultra cement 120 Mixing time, min. 9 9 9 9 10 Bulk densitykg/m³ 328 332 343 371 385Other Binders Systems and Products Comprising the Binder Systems(114-118)

Composition 112 is a hydrophobic binder system and 113 is a product inthe form of pellet or alternatively a sheet comprising Rockwool®Hulrumsfyld using the binder system of 112 which was dried and cured for6 min. in the microwave oven for 6 min. 114 is a hydrophobic bindersystem which is used in the products 115-118. 115 are sheets ofRockwool® “glued” together with the binder; dried and cured in amicrowave oven for 10 min. (70% effect). 116 and 117 are hydrophobicpellet, and 118 is a sheet prepared from the binder system 114 andRockwool® Hulrumsfyld; dried and cured in a microwave oven for 12 min.(70% effect)+5 min. (80% effect). The compositions are as shown in TableIV. All products and compositions were hydrophobic due to the content ofthe potassium methyl siliconate. TABLE IV Composition No. 112 113 114115 116 117 118 Silica slurry 500 1000 1000 (50%) Additional water 500500 Rockwool ® 100 750 Hulrumsfyld Glasuld ® 525 420 HulrumsfyldPotassium methyl 10 30 40 siliconate (42%) Composition 200 No. 112Composition 1230 1230 1236 No. 113 Bulk density 292 364 325 kg/m³ Mixingtime 10 10 10 10

The compositions 119-124 relate to products useful for dispersablefibres for easy distribution to, e.g., asphalt, paints, plastics,cement, gypsum, products for oil- and chemicals absorption. The silicaslurry and the cationic surfactant were vigorously mixed with the highspeed mixer for 5-10 min. This mixture was mixed with the fibre materialin the Kenwood mixer for 5-8 min. The compositions are shown in Table V.All compositions were hydrophobic and easily dispersable. See Table V:Composition No. 119 120 121 122 123 124 Silica slurry (50%) 1200 12001200 1200 1200 1200 Additional water 200 300 Cationic surfactant 30 6060 60 60 60 Rockwool ® Hulrumsfyld 1200 1200 600 Glasuld ® Hulrumsfyld900 Chopped paper (cellulose 600 650 fibres) Bulk density kg/m³ 426 356410 425 271 270 Mixing time (silica/cat.) 10 12 12 8 12 15

Compositions 127-134 are further examples utilising the same procedureas for compositions 119-124. Compositions 127 and 128 (fine pellets) maybe useful as growth substrate. Compositions 130 (thick paste formed intoa hydrophobic sheet) and 131 (as 130 by the viscosity was dramaticallydecreased upon addition of the siliconate) illustrate a hydrophilic andhydrophobic binder system variant, respectively. Compositions 132-133(thick pastes after 24 h) also illustrate hydrophilic binder systems.Composition 134 (thick paste before addition of siliconate, then acreamy mass) is a hydrophobic binder product. The silica slurry wasvigorously mixed for 10 min. whereby a highly viscous mass was obtained.After storage for 1 day at room temperature, the viscous mass wasvigorously mixed with potassium methyl siliconate for 10 min.Afterwards, the resulting hydrophobic binder system and the fibres weremixed in the Kenwood mixer for 9 min. The product appeared in the formof pellet which were pressed and formed into a sheet. The compositionsare shown in Table VI. TABLE VI Composi- tion No. 127 128 129 130 131132 133 134 Silica 1200 300 300 300 300 300 300 300 slurry (50%)Additional 1200 300 300 water Ca(OH)₂ 60 30 30 30 30 (38%) KOH 15 30 30Additional 300 300 300 300 135 300 300 water Rockwool ® 1200 300 300 300Hulrumsfyld Potassium 30 30 30 methyl siliconate (42%) Bulk density 383342 383 285 271 270 kg/m³ pH 8 11 10 10 10 11 11Testing of Binder Systems to Evaluate the Binding Strength Towards ShotsWith Mineral Fibre Compositions (Grit Bar Test)

Shots of mineral fibres having a diameter of 0.25-0.50 mm can be used tomake bars with dimensions 140 mm×25 mm×10 mm. In order to prepare thebars, 100 ml water-based binder mixture with 15% solids content issprayed onto and mixed with 450 g shots. The used amount of shots issufficient to prepare 8 bars. The bars are cured at 90° C. for 2 hours.

Four of the bars are broken directly (dry strength), the other four barsare place in 80° C. water for 3 hours before they are broken (wetstrength).

Binding strength is determined by breaking the bars in a standardisedmeasuring device where the clamping length is 100 mm and the velocity ofthe compressing beam is 10 mm/min. Using the clamping length and thewidth and thickness of the bars, the binding strength can be determinedin N/mm².

It is expected that the dry binding strength of the mineral fibreproducts of the present invention is at least 4 N/mm², such as at least6 N/mm², in particular at least 8 N/mm², and that the wet bindingstrength is at least 1 N/mm², such as at least 2 N/mm², in particular atleast 3 N/mm². Thus, particularly interesting embodiments of the presentinvention relates to mineral fibre products having those strengthcharacteristics.

Porous Materials

Preparation of Porous Materials 1-45

The porous materials 1-45 were prepared by mixing the individualcomponents mentioned in Table 1 into a paste or a slightly wet powderwhile stirred. The stirring was continued until a workable powdersubstance was obtained, or the stirring was continued for at the most 15min, and the resulting material was then 1) extruded and made intopellets with a diameter of 3 or 4 mm, or 2) pressed into sheets, afterwhich the pellets or sheets were allowed to harden in an atmosphere ofabout 90% relative humidity (e.g. by covering the pellets or sheets byplastic film) for 14-28 days and subsequently drying the pellets orsheets.

The pH values shown in Table 1 were determined using the followingmethod: After storage for 28 days in an atmosphere of about 90% relativehumidity, the material was ground in a mortar and 4 mg was poured into25 ml demineralised water with stirring. Stirring was continued for 6minutes after which the pH was determined.

The detailed composition of each product is specified in Table 1 below.

Preparation of Porous Materials 46-56

The porous materials 46-56 were prepared by mixing the silica slurry(50% w/w) with the fibres while stirring until a viscous paste wasformed. Perlite was then added while stirring until the texture of thematerial was “dough-like”. Cement was added under vigorous stirringwhereby a workable mass was obtained within a few minutes.

Continuing the stirring for 5-20 minutes resulted in formation of smallindividual pellets having a diameter in the range from about 1 to 8 mmdepending on the actual stirring time.

The pellets were then allowed to harden (hydraulic hardening) in anatmosphere of 100% relative humidity (e.g. by covering the pellets byplastic film) for 28 days and subsequently drying of the pellets.

The pH values shown in Table 2 were determined using the followingmethod: After storage for 28 days in an atmosphere of about 100%relative humidity, the material was grounded in a mortar and 4 mg waspoured into 25 ml demineralised water with stirring. Stirring wascontinued for 6 minutes after which the pH was determined.

The detailed composition of each of the products 46-56 is specified inTable 2 below.

Preparation of Porous Materials 57-60 and 63-76 and 83-90

The porous materials 57-60 and 63-76 and 83-90 were prepared asdescribed above (i.e. as described for the materials 46-56) except thatperlite was not added. The detailed composition of each of the products57-60 and 63-76 and 83-90 is specified in Table 2 below.

The compositions 83-87 (pellets) are derived from silica slurry,additional water and rapid cement (around 20% by weight of the silica)and various amounts of Rockwool® Hulrumsfyld. The aim with thecompositions was to prepare a cheap, well-formed, light,non-inflammable, robust pellet prepared from as little binder and excesswater as possible. These pellets could be used as constituents in thepreparation of concrete and in other matrices, for the filtration ofliquids, e.g. water, but also greasy substances in air, in particularkitchen ventilation air and diesel exhaust from motors. The slurry andadditional water and fibres were mixed in a Kenwood mixer to ahomogenous, heterogenous mass, whereafter the cement was added undercontinued mixing. After a short time of mixing a clear agglomeration wasobserved (granule formation). The time and amount of water determinesthe uniformity and size of the pellets.

The composition 88 is a pellet as above, but improved by addition ofactive carbon in powder form with the aim of removal of odoroussubstances.

The compositions 89 and 90 are similar pellets where RockwoolHulrumsfyld is replaced by Glasswool Hulrumsfyld. These pellets areapparently less dense (fibres without pearls).

Preparation of Porous Materials 61 and 62

The porous materials 61 and 62 were prepared as described above (i.e. asdescribed for the materials 46-56) except that cement was not added.Furthermore, the materials were not hardened by a hydraulic process butwere fixed (cured) by drying. The detailed composition of each of theproducts 61 and 62 is specified in Table 2 below.

Most of the porous materials (1-62) were subjected to two differentqualitative tests, the “Water absorption test” and the “Oil absorption”test, as described below.

Furthermore, most of the materials were qualitatively characterised bytheir swelling properties in water, their insolubility in water, andtheir anti-dust properties.

Water Absorption Test

About 5 g of the porous material (or activated carbon) was weighed outand added to approximately 250 ml of water. It is believed that as longas the material absorb the liquid small bubbles of air will develop dueto displacement of air in the pores of the materials. Thus, the timeuntil gas generation ceased was noted, and was taken as a qualitativemeasure of the adsorption capacity of the material in question.

Oil Absorption Test

About 2 g of white vaseline oil or vegetable oil was poured out on apiece of foil. Approximately 5 g of the material (or activated carbon)was added and the time until the oil was completely absorbed was noted,and was taken as a qualitative measure of the adsorption capacity aswell as the affinity for hydrophobic molecules. TABLE 1 Product No. 1 23 4 5 6 Dens. silica 500 490 480 462 450 350 Lime water (1%) 200 Limewater (38%) 25 50 100 150 Sand-lime mortar 150 Tap water 235 220 188 15075 Diameter (mm), pellet 3 3 3 3 3 3 pH 7.5-8 7.5-8 7.5-8 7.5-8 8.5-98.5-9 Product No. 7 8 9 10 11 12 Loose silica 325 300 Dens. silica 450425 450 Silica slurry 500 Slaked lime powder 50 75 150 Basic cement 163190 Rapid cement 50 Tap water 250 250 325 300 250 CMC powder 12 10 6Non-ionic and anionic 6 surfactants Diameter (mm), pellet 3 3 4 4 3Sheet X pH 8-8.5 8-8.5 12 8.5-9 8.5-9 7.5-8 Product No. 13 14 15 16 1718 Loose silica 240 220 220 250 250 Dens. silica 450 Rapid cement 50 120110 100 125 125 Tap water 250 240 220 220 250 250 Perlite < 7 μm 140 170125 Perlite < 14 μm 180 Wood flour 125 CMC powder 5 Non-ionic andanionic 3 surfactants Diameter (mm), pellet 3 3 3 3 3 3 pH 7.5-8 7.5-87.5-8 7.5-8 9-9.5 7.5-8 Product No. 19 20 21 22 23 24 Loose silica 99Dens. silica 350 425 100 180 225 Silica slurry 342 White cement 50 50 7550 50 50 Tap water 260 200 184 194 175 Perlite < 7 μm 270 Perlite < 14μm 180 350 225 Cryst. cellul. powder 100 Non-ionic and anionic 6 6 15 66 6 surfactants Diameter (mm), pellet 3 3 3 3 3 3 pH 7.5-8 7.5-8 7.5-87.5-8 7.5-8 7.5-8 Product No. 25 26 27 28 29 30 Loose silica 500 500Dens. silica 225 425 450 483 Lime water (1%) 225 Soda lye (27%) 60 62Soda water glass 25 White cement 50 75 Hasle cement 50 Tap water 160 225250 260 130 Perlite < 14 μm 225 CMC powder 3 Non-ionic and anionic 6 10surfactants Cat. surfact. (15%) Diameter (mm), pellet 3 4 3 3 3 Sheet XpH 7.5-8 9 7.5-8 7 9-9.5 9-9.5 Product No. 31 32 33 34 35 36 Loosesilica 500 Dens. silica 500 500 500 300 250 Soda lye (27%) 25 28 tapwater 200 175 170 150 140 Perlite < 14 μm 200 250 Non-ionic and anionic6 6 surfactants Cat. surfact. (15%) 185 10 Diameter (mm), pellet 3 3 3 33 3 pH 8.5-9 8.5-9 7-7.5 7-7.5 7.5-8 7.5-8 Product No. 37* 38 39 40 4142** 43 Loose silica 250 250 250 Dens. silica 250 450 Lime water (1%) 5l. Lime water (38%) 400 Lime water (42%) Slaked lime powder 100 50 Tapwater 140 275 335 250 200 20 l. Perlite < 14 μm 250 Cellulose fibres 250Ground straw < 250 250 250 5 μm Polymer particles 15 Non-ionic and 6anionic surfactants Diameter (mm), 3 3 3 3 4 pellet Sheet X pH 7-7.56.5-7 7 11-12 7 12 7.5-8 Product No. 44 45 Loose silica 500 Dens. silica250 Tap water 167 190 Perlite < 7 μm 250 White vaseline oil 10 Non-ionicand anionic 10 surfactants Diameter (mm), pellet 4 3 pH 7-7.5 7-7.5*burned in a gas flame for 20 min.**75 g ethanol (93%) was added.

TABLE 2 Product No. 46 47 48 49 50 51 52 Silica slurry (50%) 1100 11001100 1100 1000 1000 1100 Wheat fibre (cellulose 75 85 fibres) Cottonfibres 50 85 (cellulose fibres) Rockwool ® granules 250 250 Micro glassfibre 150 Rapid cement 100 100 100 100 100 100 100 Perlite < 7 μm 350300 300 300 300 300 Perlite < 14 μm 300 Product No. 53 54 55 56 57 58 59Silica slurry (50%) 1100 1100 1100 1200 1440 1440 1332 Tap water 180Chopped paper 70 180 200 240 (cellulose fibres) Xotton fibres 75 75(cellulose fibres) QSA D100 Food Agar 90 (cellulose fibres) Ultra cement100 Rapid cement 100 100 100 80 94 White cement 100 Active carbon 100100 Perlite < 7 μm 200 200 300 100 Perlite < 14 μm 130 pH 8-9 8-9 8-9Product No. 60 61 62 63 64 65 66 Silica slurry (50%) 1200 1000 1000 12001200 1200 1200 Tap water 400 300 300 Chopped paper 300 600 60 (cellulosefibres) SMP SR 80 60 60 60 (cellulose fibres) Rapid cement 100 90 90 9090 Active carbon 150 250 50 Perlite < 7 μm 100 200 250 Perlite < 14 μm700 pH 8-9 Bulk density kg/m³ 423 417 437 447 Water absorption 33 28 3735 %(w/w) Surface area m²/g 192 292 88 34 Evaluation of 2 3 4 3 pellets*Product No. 67 68 69 70 71 72 Silica slurry (50%) 1200 1420 1200 13001200 1100 Tap water 100 100 Chopped paper 200 (cellulose fibres) SMP SR80 80 100 80 (cellulose fibres) Cotton fibres 80 (cellulose fibres)Rapid cement 90 90 90 90 90 90 Perlite < 7 μm 250 210 180 280 Perlite0-3 mm 260 Bulk density kg/m³ 441 409 413 410 436 416 Water absorption %40 38 37 35 34 31 Surface area m²/g 39 43 43 38 37 39 Evaluation ofpellets 2 3 4 3 2 3 Product No. 73 74 75 76 Silica slurry (50%) 12001200 1200 1250 SMP SR 80 60 70 (cellulose fibres) Acrylic fibres 2 mm 52FDE Plast fibres 940T 70 Rapid cement 90 90 90 80 Perlite 0-3 mm 150 240340 150 Bulk density kg/m³ 433 399 427 439 Water absorption % 36 30 3436 Surface area m²/g 135 31 35 128 Evaluation of pellets 4 3 2 4 ProductNo. 83 84 85 86 87 88 89 90 Silica slurry 1000 1000 1000 800 910 910 9101000 (50%) Tap water 200 200 200 300 244 244 244 200 Carbon powder 50850 m²/g Rockwool ® 400 480 500 520 455 405 Hulrumsfyld Glasuld ® 455400 Hulrumsfyld Rapid cement 100 100 100 80 91 91 91 100 Bulk density375 399 386 351 373 378 330 333 kg/m³ Mixing time 7 8 8 8 8 8 12 9Evaluation of 3 4 4 4 pellets*1 poor, 2 fair, 3 good, 4 excellentDiscussion and Conclusion

In general the materials produced as shown in the examples hereinexhibited absorption properties which were superior to activated carbon.The materials produced from ultra-fine silica, water, and cement orcalcium hydroxide were especially efficient as they absorbed oil muchfaster than activated carbon when subjected to the “Oil absorptiontest”. This effect was further enhanced when the material also comprisedperlite and, in particular, when the material also comprised cellulosefibres. The above conclusion also holds true for the evaluation based onthe “Water absorption test”, where it was found that the materialsproduced from ultra-fine silica, water and cement or calcium hydroxidecontinued to evolve air-bubbles, in many cases for about 24 hours,whereas air-evolution ceased within 0.5 to 1 hour in the case ofactivated carbon.

Thus, based on the above-mentioned test, the materials produced fromultra-fine silica, water, and calcium hydroxide or cement, and/orperlite, and/or cellulose fibres exhibited a greater absorbing capacitythan activated carbon.

Furthermore, the materials were easy to handle without producing dust.They did not easily break up, and most of the materials, especiallythose produced from ultra-fine silica, water, and calcium hydroxide,and/or perlite, and/or cement, were stable in water, i.e. when subjectedto the “Water absorption test” the aqueous phase did not become turbideven after standing for 24 hours. An additional advantage of thematerials is that they are incapable to swell in an aqueous solution.Thus, when applied to the “Water absorption test” no swelling wasobserved even when standing for 24 hours.

1. A mineral fibre/particle product comprising mineral fibres and/ormineral particles and a binder system, said binder system being derivedfrom a mixture comprising amorphous silica and one or more bases, andoptionally one or more additives.
 2. A product according to claim 1,wherein the binder system is derived from a mixture comprising amorphoussilica, at least one of (a) an alkali metal organosiliconate and (b) abase.
 3. A mineral product according to claim 2, wherein the bindersystem is derived from an alkali metal organosiliconate.
 4. A mineralproduct according to claim 2, wherein the base is selected from alkalior alkaline earth metal hydroxides, alkali or alkaline earth metalsilicates, aluminium silicates, iron(II) and iron(III) silicates andmixtures thereof, alkali or alkaline earth metal pyrosilicates,aluminium pyrosilicates, iron(II) and iron(III) pyrosilicates andmixtures thereof, alkali or alkaline earth metal carbonates, alkali oralkaline earth metal bicarbonates, alkali or alkaline earth metalphosphates, alkali or alkaline earth metal pyrophosphates, ammonia,organic amines, and cements, and combinations thereof.
 5. A mineralproduct according to claim 4, wherein the base is selected from alkalimetal hydroxides, alkaline earth metal hydroxides and cements,preferably selected from sodium hydroxide, potassium hydroxide andcalcium hydroxide.
 6. A method for preparing a mineral fibre/particleproduct comprising mineral fibres and/or mineral particles and a bindersystem, said binder system being derived from an aqueous mixture ofamorphous silica, one or more bases, and optionally additives, themethod comprising the step of: preparing a binder system by vigorouslymixing an aqueous slurry of the amorphous silica, the one or more bases,and the optional additives, applying the binder system to the mineralfibres and/or mineral particles, and drying and curing the binder so asto obtain the mineral fibre/particle product.
 7. A method according toclaim 6, wherein the binder system is derived from an aqueous mixture ofamorphous silica, at least one of (a) an alkali metal organosiliconateand (b) a base, and optionally additives, and the preparation of thebinder system is performed by mixing an aqueous slurry of the amorphoussilica, with the at least one of (a) an alkali metal organosiliconateand (b) a base, and the optional additives.
 8. A method according to anyof the claims 6, wherein the pH of the binder system is in the range of7.5-11.0 upon application to the mineral fibres and/or mineralparticles.
 9. An water-based binder system comprising the reactionproduct of amorphous silica and one or more bases.
 10. A binder systemaccording to claim 9, wherein the one or more bases is at least one of(a) an alkali metal organosiliconate and (b) a base, and whichoptionally comprises one or more additives.
 11. A binder systemaccording to claim 9, which has a pH in the range of 7.5-11.0.
 12. Abinder system according claim 9, wherein the base is selected fromalkali or alkaline earth metal hydroxides, alkali or alkaline earthmetal silicates, aluminium silicates, iron(II) and iron(III) silicatesand mixtures thereof, alkali or alkaline earth metal pyrosilicates,aluminium pyrosilicates, iron(II) and iron(III) pyrosilicates andmixtures thereof, alkali or alkaline earth metal carbonates, alkali oralkaline earth metal bicarbonates, alkali or alkaline earth metalphosphates, alkali or alkaline earth metal pyrophosphates, ammonia,organic amines, and cements, and combinations thereof.
 13. A bindersystem according to claim 9, wherein the base is selected from alkalimetal hydroxides, alkaline earth metal hydroxides and cements,preferably selected from sodium hydroxide, potassium hydroxide andcalcium hydroxide.
 14. A method for preparing a binder system derivedfrom a mixture comprising amorphous silica, one or more bases, andoptionally additives, the method comprising vigorously mixing an aqueousslurry of the amorphous silica with the one or more bases, and theoptional additives.
 15. A mineral fibre/particle product according toclaim 1 comprising mineral fibres and/or mineral particle and a bindersystem, said binder system being derived from a mixture comprisingamorphous silica and potassium hydroxide, and optionally one or moreadditives, the stoichiometric ratio of amorphous silica to potassiumhydroxide being 1:<1.
 16. A method according to claim 6, wherein thebase is selected from alkali metal hydroxides, alkaline earth metalhydroxides and cements, preferably selected from sodium hydroxide,potassium hydroxide and calcium hydroxide.
 16. A method according toclaim 6 for preparing a mineral fibre/particle product comprisingmineral fibres and/or mineral particle and a binder system, said bindersystem being derived from a mixture comprising amorphous silica andpotassium hydroxide, and optionally additives, the method comprising thesteps of: preparing a binder system by mixing an aqueous slurry of theamorphous silica with potassium hydroxide and the optional additives,the stoichiometric ratio of amorphous silica to potassium hydroxidebeing 1:<1, applying the binder system having a pH of 7.5-11.0 to themineral fibres and/or mineral particles, and drying and curing thebinder so as to obtain the mineral fibre/particle product.